Optimizing 802.11 power-save for IP multicast groups

Abstract

A method for providing a superior quality of service for multicast data streams delivered over a wireless local area network. As Internet Protocol multicast data streams are received by an access point, the access point observes Internet Group Multicast Protocol registration messages to determine which of its associated stations subscribe to each multicast data stream. The access point then determines which of the multicast data streams it receives have only active subscribing stations as opposed to those data streams having at least one associated station operating in power-save mode. The access point will automatically transmit each multicast data stream having only active subscribers immediately to the associated active stations, while buffering the multicast data stream for which there is at least one associated station operating in power-save mode.

The invention claimed is: 
     
       1. An apparatus, comprising:
 an access point configured to wirelessly communicate with at least one mobile device; 
 wherein the access point is configured to determine a multicast group membership for a first Internet Protocol (IP) multicast group and a second IP multicast group; 
 the access point determines whether members of the first IP multicast group are in an active state or a power save state; 
 the access point determines whether members of the second IP multicast group are in an active state or a power save state; 
 wherein the access point receives a multicast packet for the first and second IP multicast groups; 
 wherein the access point is configured to send the multicast packet to the first multicast group without waiting for a beacon responsive to determining that none of the members of the first IP multicast group are currently in the power save state; and 
 wherein the access point is further configured to buffer the multicast packet and send the multicast packet to the second IP multicast group after a subsequent beacon responsive to determining that at least one member of the second IP multicast group is in the power save state. 
 
     
     
       2. The apparatus of  claim 1 , wherein the access point is an 802.11 access point. 
     
     
       3. The apparatus of  claim 1 , wherein the access point determines the multicast group membership for a mobile device by observing an Internet Multicast Group Protocol join request transmitted by the mobile device. 
     
     
       4. The apparatus of  claim 1 , wherein the access point determines a first mobile device is currently able to accept a multicast packet responsive to the first mobile device being a low-latency station. 
     
     
       5. The apparatus of  claim 1 , wherein a multicast data stream is transmitted to a plurality of stations operating on a same virtual local area network. 
     
     
       6. The apparatus of  claim 1 , wherein a multicast data stream is transmitted to a plurality of stations operating on a plurality of virtual local area network. 
     
     
       7. The apparatus of  claim 1 , wherein the access point buffers the packet and sends the packet after a subsequent beacon responsive to determining at least one recipient of the packet supporting only high packet delivery latency. 
     
     
       8. The apparatus of  claim 1 , wherein the access point immediately sends the packet responsive to determining all recipients of the packet support only low packet delivery latency. 
     
     
       9. The access point of  claim 1 , wherein the access point determines a member of the multicast group is unable to receive a frame if the member is in a power save mode. 
     
     
       10. A method, comprising:
 determining members of a first Internet Protocol (IP) multicast group; 
 determining members of a second IP multicast group; 
 receiving a multicast packet for the first and IP multicast groups; 
 determining whether the members of the first IP multicast group are currently in an active state or a power save state; 
 determining whether members of the second IP multicast group are currently in the active state or the power save state; 
 sending the multicast packet to the first IP multicast group without waiting for a beacon responsive to determining that none of the members of the first IP multicast group are in the power save state; and 
 buffering and sending the packet after a subsequent beacon to the second IP multicast group responsive to determining a member of the second IP multicast group is unable to receive the second multicast packet. 
 
     
     
       11. The method of  claim 10 , wherein a plurality of mobile devices belong to the first IP multicast group, the method further comprising:
 determining whether any members of the first IP multicast group are in a power save mode; 
 sending a multicast packet to the IP multicast group without waiting for a beacon responsive to determining none of the members of the IP multicast group are in the power save mode. 
 
     
     
       12. Logic encoded in a non-transitory tangible computer readable media for execution, and when executed operable to:
 determine members of a first Internet Protocol (IP) multicast group; 
 determine members of a second IP multicast group; 
 receive a multicast packet for distribution to both first and IP multicast groups; 
 determine whether the members of the first IP multicast group are in an active state or a power save state; 
 determine whether members of the second IP multicast group are currently in the active state or the power save state; 
 send the multicast packet to the first IP multicast group without waiting for a beacon responsive to determining that no members of the first IP multicast group are in the power save state; and 
 buffer and send the packet after a subsequent beacon to the second multicast IP group responsive to determining a member of the second IP multicast group is in the power save state.